1. Field of the invention
The invention relates generally to avionics equipment, such as flight recorders. More particularly, the invention relates to a back up power supply for avionics equipment that can be installed in existing equipment trays located for example, but not exclusively, in the tail section of an aircraft, without having to rewire the aircraft.
2. State of the Art
The state-of-the-art is best introduced with the excerpts and paraphrases from the National Transportation Safety Board, Safety Recommendation A-99-16-18, dated Mar. 9, 1999.
Although the recommendations set forth hereinafter are directed to back up power supplies for cockpit voice recorders (CVR""s) per se; those skilled in the art will readily appreciate that back up power supplies may be useful to power other types of avionics equipment should power from the aircraft""s power supply be lost. Hence reference hereinafter to CVR""s is intended for illustrative purposes only; and not to limit the scope of the invention described and claimed herein.
Many recent aircraft accidents have illustrated the need for an xe2x80x9cindependentxe2x80x9d back-up power supply for the aircraft CVR. As used herein, the word xe2x80x9cindependentxe2x80x9d means independent from the aircraft power supply, not necessarily independent from the CVR unit.
For example, on May 11, 1996, the crew of ValuJet flight 592, a DC-9-32, reported smoke and fire shortly after departing Miami, Fla. The flight recorders stopped about 40 to 50 seconds before the airplane crashed on its return to the airport.
On Jul. 7, 1996, TWA flight 800, a Boeing 747-100, on an international passenger flight from New York to Paris, exploded about 13 minutes after takeoff as it was climbing through 13,700 feet. Both flight recorders stopped at the time of the explosion, but the airplane did not hit the water off Long Island, N.Y., for another 40 to 50 seconds.
On Dec. 19, 1997, SilkAir flight 185, a Boeing 737, entered a rapid descent from 35,000 feet, which ended with a high speed impact in the Sumatran River near Palembang, Indonesia. The Indonesian investigation determined that both flight recorders stopped prior to the airplane entering the rapid descent.
On Sep. 2, 1998, Swissair flight 111, an MD11, on a regularly scheduled passenger flight from New York to Geneva, Switzerland, diverted to Halifax after the crew reported smoke in the cockpit; the airplane crashed into the waters near Peggy""s Cove, Nova Scotia. Thus far, the Canadian Transportation Safety Board""s (TSB) investigation has been severely hampered by the lack of data from the cockpit voice recorder (CVR), which stopped nearly 6 minutes before the airplane hit the water.
These recent accidents are just the latest in a long history of accident and incident investigations that were hindered by the loss of flight recorder data due to the interruption of aircraft electrical power.
Since 1983, the origin date of the NTSB database, there have been 52 accidents and incidents, including the 4 recent accidents mentioned above, in which information from either a CVR or FDR (flight data recorder) or both were lost due to interruption of electrical power following an engine or generator failure or crew action. Until recently, recorder technology did not offer a practical solution to the problem of loss of electrical power to the on-board recorders. However, recent innovations in recorder and power supply technologies have made it possible to provide an independent power source that would provide sufficient power to operate a solid-state flight recorder for a predetermined period of time, for example, 10 minutes.
In assessing the feasibility of an independent power source, strong consideration must be given to reliability, complexity, maintainability, and cost. The independent power source must also automatically engage when power to the recorders is lost; and disengage after a predetermined period of time so as not to overwrite recorded data.
Older model tape-based recorders require too much electrical power and are not easily adapted to a direct current (d.c.) battery or capacitor. However, the relatively low power requirements of solid-state flight recorders (about 10 to 12 watts from a 28-volt d.c. system) would permit the use of an independent power source. Thus, it is evident that the use of an independent power source would also require the use of solid-state flight recorders.
Current regulations call for a CVR with a minimum 30-minute recording duration. This minimum requirement was based on the limitations of 1960s recorder technology, which was constrained by the amount of magnetic tape that could be impact/fire protected.
In the years since CVRs became mandatory, the Safety Board has investigated many accidents and incidents for which the 30-minute CVR recording was not sufficient to retain key events. This prompted the Safety Board to recommend in 1996 that all newly manufactured CVRs be SSCVRs (solid state CVRs) with a 2-hour recording duration (Safety Recommendation A-96-171). Accident investigations in which the Safety Board has participated subsequent to the issuance of Safety Recommendation A-96-171 continue to demonstrate that a lack of recorded voice and other aural information can inhibit safety investigators and delay or prevent the identification of safety deficiencies.
The CVR installed on Swissair flight 111 used a continuous-loop magnetic tape with a 30-minute duration. The earliest information on the CVR tape was recorded about 15 minutes before the crew noted an unusual odor. Crew conversations and cockpit sounds prior to the beginning of this 30-minute recording might have provided insight into any initiating or precursory events that led to the accident.
About 38 minutes prior to the crew noting an unusual odor, Boston Center issued flight 111 a radio frequency change. During the following 13 minutes, Boston Center made repeated attempts to contact flight 111 but did not establish contact. Any cockpit conversations, flight deck noises, or attempted crew transmissions that occurred during this period were subsequently overwritten on the CVR, and thus were not available to the accident investigators.
Although 30-minute magnetic tape CVRs are no longer being manufactured, units still exist and could be installed on aircraft today. Given the continued need for longer periods of recorded sound to capture the initiating events of aviation accidents, and the availability of and trend toward 2-hour CVRs, the Safety Board has stated that a retrofit program is warranted.
The Safety Board has further stated that the Federal Aviation Administration (FAA) should require the retrofit after Jan. 1, 2005, of all CVRs on all airplanes required to carry both a CVR and a FDR with a CVR that meets TSO C123a and is capable of recording the last 2 hours of audio.
A number of options have been identified for realizing an independent power source. In assessing the feasibility of these options, batteries and capacitors appear to be the most effective means of providing aircraft independent power. These and other power sources may be selected by those skilled in the art based on various well known design criteria and objectives. For example, the capacitor method would provide a power source that requires very little maintenance when compared with a rechargeable battery since, unlike a rechargeable battery, the capacitor method would not require any power sensing circuitry for normal operation. Nevertheless, total package weight, center of gravity, packaging constraints (dimensional), etc., will all factor in when selecting among the possible candidates for an independent power supply.
To maximize recorder reliability and to minimize any crew intervention, the independent power source should automatically engage whenever the normal electrical power to the recorder ceases, even when the aircraft is powered down normally. To increase the probability of recording accident data, the independent power source should be capable of powering the recorder for 10 minutes after main power to the recorder shuts off; and again, be capable of automatic shut down after a predetermined period of time to avoid overwriting data.
In the case of a CVR, the area microphone is powered by the CVR; as long as the CVR receives power, the area microphone will continue to operate and the CVR will continue to record sounds from the area microphone, provided that the connection between the microphone and the recorder is not compromised.
In the case of the SilkAir accident, the 2-hour SSCVR stopped recording 5 minutes 58 seconds prior to the DFDR (digital flight data recorder) stopping, which stopped 1 minute 54 seconds prior to impact. Thus, any valuable dialog in the cockpit regarding the airplane status for those 7 minutes 52 seconds was lost. However, providing a 30-minute CVR with 10 minutes of independent power after main power ceases would result in about one-third of the in-flight audio being recorded over. Thus, it would not be acceptable to fit 30-minute CVRs with an independent power supply that automatically engages when aircraft electrical power is terminated for any reason.
With maintenance-free independent power sources, it is now feasible to provide an independent power source for new-technology CVRs for a specific period of time, in the event that aircraft power sources to the CVR are interrupted or lost.
Accordingly, the Safety Board recommended that for the CVR retrofit after Jan. 1, 2005, the FAA should also require the CVR to be provided with an independent power source that is located with the CVR and that automatically engages and provides 10 minutes of operation whenever aircraft power to the recorder ceases, either by normal shutdown or by a loss of power to the bus.
The Canadian Transportation Safety Board (TSB) shares the view that a CVR retrofit is warranted and has developed a similar recommendation, which was issued to the Canadian and European regulators in early March 1999. The Safety Board and the TSB have urged that the actions recommended by the two investigative authorities be adopted by civil aviation regulators worldwide.
Accordingly, the National Transportation Safety Board has recommended that the Federal Aviation Administration: Require retrofit after Jan. 1, 2005, of all cockpit voice recorders (CVRS) on all airplanes required to carry both a CVR and a flight data recorder (FDR) with a CVR that (a) meets Technical Standard Order (TSO) C123a, (b) is capable of recording the last 2 hours of audio, and (c) is fitted with an independent power source that is located with the digital CVR and that automatically engages and provides 10 minutes of operation whenever aircraft power to the recorder ceases, either by normal shutdown or by a loss of power to the bus.
Although the aforementioned recommendations are directed to CVR""s specifically, back up power supplies which can be installed in existing equipment storage racks, do not require rewiring the aircraft, are easy to maintain and test, etc., would be useful for providing a back up power source for other types of avionics equipment including, for example, FDR""s, etc.
Accordingly, although the invention will be described hereinafter with reference to an illustrative embodiment thereof (a modular back up power supply for a CVR), the scope of the invention is not intended to be limited thereby, i.e., the invention covers back up power supplies for avionics equipment in general; modular or not.
Furthermore, although the recommendations of the NTSB are quite specific; and although the DOT and ARINC have issued detailed specifications for the new CVRs, many questions still remain as to how to provide the recommended back up power supply, how the back up power supplies will be installed in the confines of an aircraft where space and other constraints limit where and how to locate and install such units; etc.
For example, will it be necessary to rewire at least some portion of the aircraft to install a back up power supply? Will it be further necessary to rewire the aircraft so that the CVR and it""s back up power supply may be tested from the cockpit? Will it be necessary to require and/or reconfigure the equipment storage racks in order to accommodate the back up power supply and a CVR?
It should be noted that industry has recommended that any separate power supply be located outside the existing equipment racks. This recommendation is problematic in that additional space in the aircraft is required; safety and aircraft rewiring become issues if external wiring is required to couple rack mounted equipment to a back up power supply unit located outside a rack; where to locate mounts for the power supplies becomes an issue; the weight of the added independent power supply units needs to be considered, etc.
Accordingly, and notably in addition to the aforementioned recommendations, it would be desirable to be able to provide a back up power supply unit for avionics equipment which, together with the avionics equipment, can use existing racks.
It would be further desirable to be able to provide a back up power supply that does not require an independent mechanical mount in the confines of the aircraft.
Further still, it would be desirable to provide a back up power supply that does not require any aircraft rewiring.
It would also be desirable to provide a back up power supply/avionics equipment combination that has a combined weight that is less than or equal to the weight of a piece of conventional (not backed up) avionics equipment alone.
Still further, it would be desirable to provide a modular back up power supply for use with avionics equipment to allow for easy installation and testing of the back up unit independent (where the modular design is used) of the avionics equipment being powered. This would avoid having to re-test an integrated back up power supply/avionics equipment combination to meet all the specs of the avionics equipment (if opened), as would be the case where an integrated unit (which also comes within the scope of the invention) is used.
Further yet, it would be desirable to provide a module fault reporting capability for both a back up power supply module and avionics equipment module, using the existing wiring for reporting equipment module faults; and to provide a xe2x80x9cpush to testxe2x80x9d feature for testing either (or both) of the back up power supply module and equipment backed up, using the existing cockpit button and electrical connection to a rack presently used to test the equipment (not backed up) alone.
It is therefore a primary object of the invention to provide a back up power supply for avionics equipment in general.
It is a more specific object of the invention to provide a tray adapted back up power supply for avionics equipment in general, i.e. a back up power supply unit for avionics equipment which, together with the avionics equipment, can use existing racks.
It is a further object of the invention to provide a back up power supply for avionics equipment that does not require additional wires or cables to couple the power supply to the equipment.
Furthermore, it is an object of the invention to provide a back up power supply that does not require any aircraft rewiring.
Further still, it is an object of the invention to be able to provide a back up power supply that does not require an independent mechanical mount in the confines of the aircraft.
It is also an object of the invention to provide a back up power supply/avionics equipment combination that has a combined weight that is less than or equal to the weight of a piece of conventional (not backed up) avionics equipment alone.
Still further, it is an object of the invention to provide a modular back up power supply for use with avionics equipment to allow for easy installation and testing of the back up unit independent (where the modular design is used) of the avionics equipment being powered.
Further yet, it is an object of the invention to provide a module fault reporting capability for both a back up power supply module and avionics equipment module, using the existing wiring for reporting equipment module faults; and to provide a xe2x80x9cpush to testxe2x80x9d feature for testing either (or both) of the back up power supply module and equipment backed up, using the existing cockpit button and electrical connection to a rack presently used to test the equipment (not backed up) alone.
It is also an object of the invention to provide a cockpit voice recorder (CVR) with an independent power supply.
Still another object of the invention is to provide a CVR having an independent power supply which meets the requirements and recommendations of the NTSB, DOT, and ARINC.
It is another object of the invention to provide a CVR having an independent power supply which does not require any rewiring of an aircraft in order that the backed up avionics equipment (e.g., a CVR) and independent power supply be tested from the cockpit.
It is also an object of the invention to provide an independent power supply which does not occupy an undue amount of space.
It is still another object of the invention to provide a CVR and independent power supply which is retro-fittable into the existing equipment rack which now receives a prior art CVR.
It is also an object of the invention to provide an independent power supply which does not require an independent mechanical mount in the confines of the aircraft.
It is still another object of the invention to provide a CVR and independent power supply which has a similar weight and center of gravity as the existing CVRs.
It is also an object of the invention to provide a modular back up power supply which is easy to install and test.
It is still another object of the invention to provide a CVR and independent power supply which utilize the existing xe2x80x9cpush to testxe2x80x9d circuits in the cockpit.
Further still, it is an object of the invention to provide methods for providing back up power for avionics equipment in accord with the aforestated objects.
In accord with these and other objects of the invention, which will be discussed in detail below, the backup power supply for avionics equipment will be described with reference to an illustrative embodiment, namely a cockpit voice recorder and independent power supply.
The cockpit voice recorder and independent power supply of a preferred embodiment of the present invention includes separate, modular CVR and power supply units. The power supply is designed to fit into a conventional CVR tray and the new CVR is designed to fit into the power supply. The combination is designed to fit within approximately the footprint and space occupied by a xe2x80x9cconventionalxe2x80x9d CVR as defined hereinafter (including specific dimensions being set forth), with reference to the description of the illustrative prior art tray and CVR shown in FIGS. 1-6.
According to the preferred embodiment of the invention, the power supply is xe2x80x9cplug compatiblexe2x80x9d with the existing electrical connector in the existing CVR tray and includes circuitry which allows both the power supply and the CVR to be tested using the existing CVR test button in the cockpit. Moreover, for safety purposes, the power supply includes circuitry which automatically electrically disconnects it from the CVR and exposed pins when the power supply is removed from the existing CVR tray.
Furthermore, according to a preferred embodiment of the invention, the power supply utilizes the same xe2x80x9cpush to testxe2x80x9d circuitry as the existing CVRs; and the same wiring used to output fault indications from the recorder alone are used to output fault indications from both the power supply and recorder (whether modular units or integrated as one device).
The invention also contemplates methods for providing a back up power supply for avionics equipment, comprising the steps of: (a) utilizing a back up power supply that includes a self contained power source; (b) combining said back up power supply with the avionics equipment such that the combination of equipment fits into a conventional equipment tray; and (c) retrofitting the combination of said power supply and said avionics equipment into a conventional equipment tray without rewiring the aircraft.
Further methods contemplated by the invention include the steps of: (a) fabricating a back up power supply module, including a self contained power source, that is plug compatible with a conventional tray avionics equipment connector; and (b) fabricating said power supply module to be plug compatible with said avionics equipment, the combination of said power supply and said avionics equipment being able to fit substantially within said tray.
The CVR and power supply of the present invention are preferably (though not necessarily) modular, easy to install, require no cables, occupy approximately the same space previously occupied by the existing CVR, and have substantially the same center of gravity as the existing CVR.
Again, although the presently preferred embodiment includes separate CVR and power supply modules, the invention contemplates and encompasses a single integrated unit which fits into an existing equipment rack.
Further advantages and features of the invention include providing a back up power supply unit for avionics equipment which, together with the avionics equipment, can use existing racks; a back up power supply that does not require an independent mechanical mount in the confines of the aircraft; a back up power supply that does not require any aircraft rewiring; a back up power supply/avionics equipment combination that has a combined weight that is less than or equal to the weight of a piece of conventional (not backed up) avionics equipment alone; a modular back up power supply for use with avionics equipment to allow for easy installation and testing of the back up unit independent (where the modular design is used) of the avionics equipment being powered; a module fault reporting capability for both a back up power supply module and avionics equipment module, using the existing wiring for reporting equipment module faults; and to provide a xe2x80x9cpush to testxe2x80x9d feature for testing either (or both) of the back up power supply module and equipment backed up, using the existing cockpit button and electrical connection to a rack presently used to test the equipment (not backed up) alone.
Additional objects and advantages of the invention will become apparent to those skilled in the art upon reference to the detailed description taken in conjunction with the provided figures.